1. Field of the Invention
The present invention relates to a control apparatus for an internal combustion engine, and more particularly to fuel injection control at the time of startup of an internal combustion engine provided with a first fuel injection mechanism (in-cylinder injector) for injecting fuel into a cylinder (into a combustion chamber) and a second fuel injection mechanism (intake manifold injector) for injecting fuel into an intake manifold and/or an intake port.
2. Description of the Background Art
An internal combustion engine having an in-cylinder injector for injecting fuel directly into a combustion chamber and an intake manifold injector for injecting fuel into an intake port (intake manifold) of each cylinder has been proposed. A control apparatus for such an internal combustion engine that carries out fuel injection using both of the in-cylinder injector and the intake manifold injector during a homogeneous combustion operation has also been proposed (e.g., Japanese Patent Laying-Open No. 2002-364409; hereinafter, referred to as “Patent Document 1”). In particular, Patent Document 1 discloses a configuration where fuel injection via the in-cylinder injector is ensured so as to suppress fuel deposition therein due to an increase in temperature of its tip end.
Meanwhile, in the engine cold state, vaporization of the fuel inside the cylinder is unlikely to be promoted. Thus, if fuel is injected via the in-cylinder injector, a large quantity of the fuel may deposit on the top surface of the engine piston and on the inner peripheral surface of the cylinder. The fuel thus deposited may degrade the exhaust emission performance due to occurrence of graphite or increase of unburned components, or may degrade the lubrication performance due to mixing with the lubricating oil of the engine piston. Therefore, it is preferable to avoid fuel injection via the in-cylinder injector during the engine cold state.